Percy is the street name for a very bad case of HPV virus, otherwise known as genital warts. Percy looks like skin tags, or raised moles, but are on the genital area, or the anus. Some descriptions are that they look like small califlower clusters, except they are not white. If you want to see a picture of them, go to Yahoo images, and put in the keyword genital warts.

Nick caught percy from his slutty girlfriend. Then he boinked her again trying to give them back to her, and she gave him a double dose.

Genital warts. Fine if you are a male, because you can see them, but a female with percy is very dangerous because her warts are hidden up in her wee wee

First man: I hear that girl has a very bad case of percy, and she gave warts to her new boyfriend. Now he has them all over his penis, and his tongue.
Second man: oh shit, it couldn't have been that good to risk that.
First man: Dude, he couldn't see them. They were up inside her stink.

A Percy will be a loyal amazing friend. He will respect you. You will feel like you trust him with his life when around him. He will always be a great boyfriend, brother, and also he will always be up for a good time. And he is daring and hilarious. People always miss him when he isn't present. He is always good looking and never looks bad

'Percy' is short form for personal, but has been injected into the definition of 'legit, good shit and unreal' (usually pertaining to drugs).
This is because drug dealers keep the best stuff for themselves, a drug dealer's 'percy' weed is the best weed they have. Really baked stoners deciced to confuse everyone by calling good weed percy, cause they are fucked.